In situ formation of organosulfide-metal complexes in cathode for lithium battery

Abstract

Molecular organosulfides as a class of cathode materials have the advantages of high capacity and sustainability. However, they could dissolve in organic liquid electrolytes resulting in capacity decay upon cycling. Herein, we report a strategy to anchor 1,2-benzenedithiolate (1,2-BDT) molecule as an example from dissolution by forming organosulfide-metal complex in situ in the cathode of a lithium battery. Copper nanowires (Cu NWs) are synthesized hydrothermally and then interweaved with carbon nanotubes as the current collector. Lithium 1,2-benzenedithiolate (1,2-LBDT) catholyte is added in the current collector and evaluated in a lithium half cell. In the first charge, 1,2-LBDT is converted to 1,2-BDT radicals which react with Cu NWs forming copper benzene-1,2-dithiolato complex Cu[Cu-(BDT)2]. Cu NWs are consumed and the formed Cu[Cu-(BDT)2] is hardly dissolved in the electrolyte. The whole process is revealed by Raman, X-ray diffraction, and quadrupole time-of-flight mass spectrometry and the redox mechanism is proposed. The cell exhibits a sloping discharge voltage profile with four visible plateaus, initial discharge capacity of 211.8 mAh g−1, and 1000 cycles at 0.5 C rate.